Clearing Aggregations

When using DTrace to build simple monitoring scripts, you can periodically clear the
values in an aggregation using the clear function. This function takes an aggregation
as its only parameter. The clear function clears only the aggregation's values; the
aggregation's keys are retained. Therefore, the presence of a key in an aggregation
that has an associated value of zero indicates that the key had a non-zero
value that was subsequently set to zero as part of a clear. To
discard both an aggregation's values and its keys, use the trunc. See Truncating aggregations
for details.